Datasheet
PCM1789
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.............................................................................................................................................. SBAS451A – OCTOBER 2008 – REVISED JANUARY 2009
DEC HEX B7 B6 B5 B4 B3 B2 B1 B0
23 17 RSV RSV RSV RSV RSV RSV RSV RSV
24 18 ATDA17 ATDA16 ATDA15 ATDA14 ATDA13 ATDA12 ATDA11 ATDA10
25 19 ATDA27 ATDA26 ATDA25 ATDA24 ATDA23 ATDA22 ATDA21 ATDA20
RSV Reserved
Reserved; do not use.
ATDAx[7:0] Digital attenuation level setting
Where x = 1 to 2, corresponding to the DAC output (VOUTx).
Both DAC outputs (VOUTL and VOUTR) have a digital attenuation function. The attenuation level
can be set from 0 dB to R dB, in S-dB steps. Changes in attenuator levels are made by
incrementing or decrementing one step (S dB) for every 8/f
S
time interval until the programmed
attenuator setting is reached. Alternatively, the attenuation level can be set to infinite attenuation
(or mute). R (range) and S (step) is – 63 and 0.5 for DAMS = 0, and – 100 and 1.0 for DAMS = 1,
respectively. The DAMS bit is defined in register 22 (16h). Table 15 shows attenuation levels for
various settings.
The attenuation level for each channel can be set individually using the following formula:
Attenuation level (dB) = S × (ATDAx[7:0]
DEC
– 255)
where ATDAx[7:0]
DEC
= 0 through 255.
For ATDAx[7:0]
DEC
= 0 through 128 with DAMS = 0, or 0 through 154 with DAMS = 1, attenuation
is set to infinite attenuation (mute).
Default value: 1111 1111.
Table 15. Attenuation Levels for Various Settings
ATDAx[7:0] ATTENUATION LEVEL SETTING
BINARY DECIMAL DAMS = 0 DAMS = 1
1111 1111 255 0 dB, no attenuation (default) 0 dB, no attenuation (default)
1111 1110 254 – 0.5 dB – 1 dB
1111 1101 253 – 1.0 dB – 2 dB
... ... ... ...
1001 1100 156 – 45.9 dB – 99 dB
1001 1011 155 – 50.0 dB – 100 dB
1001 1010 154 – 50.5 dB Mute
... ... ... ...
1000 0010 130 – 62.5 dB Mute
1000 0001 129 – 63.0 dB Mute
0000 0000 128 Mute Mute
... ... ... ...
0000 0000 0 Mute Mute
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